1. Field of the Invention
The present invention relates to portable commercial-grade agricultural sprayers and, more particularly, to a portable backpack-style manual-pump-operated agricultural sprayer for spraying through a hand-carried spray wand any of a variety of different chemicals from modular containers seated in a backpack housing.
2. Description of the Background
There are a wide variety of sprayers available for application of liquid fertilizers and pest control solutions, including backpack sprayers, hand sprayers, and truck-mounted spray tank systems. The simplest sprayers are designed for consumer use and typically comprise a single container with a piston pump and hand-carried wand. However, these sprayers are typically one or two gallons in size and are meant for simply maintaining a lawn or garden. The lawn and landscape industry demand more efficient commercial-grade sprayers for multiple and larger jobs, and backpack sprayers have become standard equipment in most commercial operations. Backpack sprayers afford great mobility for larger jobs on terrain where stationery equipment can't go. Backpack sprayers typically use a polyethylene plastic chemical-holding tank with a capacity of up to four gallons, with an attached shoulder harness and hand-carried spray wand.
Although motorized-pump backpack sprayers or gas cartridge (CO2) powered sprayers exist, the most popular commercial-grade sprayers are manually powered backpack-style sprayers in which the chemical-holding tank is equipped with a pump and pumping lever. The chemical-holding tank itself is not typically pressurized by the pump, but rather each tank has a smaller, pressurizing chamber. Liquid is carried from the chemical-holding tank to the pressurizing chamber by the pump, where the chemical remains until the operator squeezes a trigger-valve on the spray wand. Several pump types are available, but the two most common are piston and diaphragm pumps.
Relatively high pressures can be reached with manual backpack sprayers, although most operate at 15 to 95 psi. However, since pressure gradually decreases as the tank empties and spray is applied, the operator must periodically pump the device to make sure that pressure remains constant and that enough flow reaches the nozzle at the desired pressure.
Such backpack sprayers are not new. They date back at least to 1888 (as per U.S. Pat. No. 383,261). However, more recently backpack sprayers have grown in popularity and a number of patents have issued for design improvements.
For example, U.S. Pat. No. 2,162,057 to Brandt issued Jun. 13, 1939 shows a backpack sprayer having a tank with internal accumulator. A hand-operated piston pump pumps liquid from the container tank to the pressure vessel. As liquid is pumped in from the bottom, the air inside is compressed at the top and this provides a pressure source for discharging the liquid out from the spray nozzle.
U.S. Pat. No. 5,335,853 to Wirz issued Aug. 9, 1994 shows a backpack sprayer similar to the '057 patent to Brandt but incorporating a double-acting piston pump. Upon reciprocation of the piston either direction there is pumping of liquid from the container tank to the pressure vessel.
U.S. Pat. No. 5,284,300 to Gries et al. issued Feb. 8, 1994 shows a portable spray system with backpack carriage containing two water storage containers.
U.S. Pat. No. 5,636,791 to Leer (Gilmour, Inc.) issued Jun. 10, 1997 shows a backpack sprayer with an adjustable valve 43 that allows the operator to adjust the pressure release valve 42 of the container to a specific pressure.
U.S. Pat. Nos. 5,755,361 and 5,857,618 both to Restive et al. (D.B. Smith, Inc.) issued May 26, 1998 and Jan. 12, 1999, respectively shows a backpack pump sprayer with an expanding accumulator pump (internal balloon-like bladder) that elastically ejects liquid.
U.S. Pat. No. 7,793,804 by McGiveron (Chapin Manufacturing, Inc.) issued Sep. 14, 2010 shows a dual-action pump assembly for sprayers that overcomes a “hydrolock” problem caused by residual chemical by a one-way valve that lets in additional air during the suction part of the cycle.
U.S. Pat. No. 7,556,210 to Mandell et al. issued Jul. 7, 2009 shows a portable mixing sprayer in a wheeled or motorized unit.
R&D Sprayers produces its Model 315FG (Flash Gordon Model) which is a backpack sprayer designed to dispense from multiple bottles using CO2 cylinder pressurization.
While these prior art devices are useful to a degree, they still suffer from certain drawbacks in that they do not provide sufficient durability and reliability without materially adding to the cost or weight of the device. The primary design goals of any manual pump-operated backpack sprayer are performance, reliability, durability, ease of use, light weight, low cost, and ease of manufacture. In addition, one notable problem with conventional manual pump-operated backpack sprayers has been the difficulty in changing chemicals. A typical lawn care treatment may require application of several different chemicals successively, and upon each changeover of chemical the sprayer tank must be drained and refilled. This is cumbersome and if not done thoroughly there is a high propensity for cross-contamination. Some chemicals, notably broad-leaf herbicides, can be difficult to fully rinse from spray tanks due to their affinity for the plastic. Moreover, residual chemicals typically remain in the compression chamber, sprayer wand and/or hose. Operators are forced to fully wash the inside of the sprayer tank and flush all internal components between applications, and this is very tedious. Still, if any residual remains serious problems can result. Upon the next successive application of fertilizer after a herbicide, any residual herbicide will have the opposite intended effect of the fertilizer. Many operators keep separate sprayers for separate chemicals for this very reason. Thus, of course, is redundant and expensive, and so what is needed is an improved portable backpack-style manual-pump-operated agricultural sprayer for spraying a variety of different and/or mixed chemicals from modular containers all seated in a backpack housing, through a hand-carried spray wand. It would be even more advantageous to provide such a sprayer with back-flush capability to clear the sprayer wand and hose upon changeover, thereby reducing or eliminating risk of cross-contamination.